Abstract
BACKGROUND: Although positive psychology interventions (PPIs) show beneficial effects on mental health in non-clinical populations, the current literature is inconclusive regarding its effectiveness in clinical settings. We aimed to examine the effects of PPIs on well-being (primary outcome), depression, anxiety, and stress (secondary outcomes) in clinical samples with psychiatric or somatic disorders. METHODS: A systematic review and meta-analysis was conducted following PRISMA guidelines. PsycINFO, PubMed, and Scopus were searched for controlled studies of PPIs in clinical samples between Jan 1, 1998 and May 31, 2017. Methodological quality of each study was rated. We used Hedges' adjusted g to calculate effect sizes and pooled results using random-effect models. RESULTS: Thirty studies were included, representing 1864 patients with clinical disorders. At post-intervention, PPIs showed significant, small effect sizes for well-being (Hedges' g = 0.24) and depression (g = 0.23) compared to control conditions when omitting outliers. Significant moderate improvements were observed for anxiety (g = 0.36). Effect sizes for stress were not significant. Follow-up effects (8-12 weeks), when available, yielded similar effect sizes. Quality of the studies was low to moderate. CONCLUSION: These findings indicate that PPIs, wherein the focus is on eliciting positive feelings, cognitions or behaviors, not only have the potential to improve well-being, but can also reduce distress in populations with clinical disorders. Given the growing interest for PPIs in clinical settings, more high quality research is warranted as to determine the effectiveness of PPIs in clinical samples. TRIAL REGISTRATION: PROSPERO CRD42016037451.